Production of blasting charges for use in substantially vertical boreholes and apparatus for use therein



Dec- S, 1962 J. E. LAMBERT ETAL 3,058,791

PRODUCTION OF BLASTING CHARGES vFOR USE IN SUBSTNTIALLY VERTICAL BOREHOLES AND APPARATUS FOR USE THEREIN Filed Feb. 4, 1957 van Ebbfll Patented Dec. 18, 1952 dce -RQBUCTIN @F BLASNG CHARGES FR USE EN -SUBSTANHLLY VERTESAL BREHLES AND Allli-t-.RAUS ,FR ESE THERElN .lames @du rrd Lambert and ida/al Gwen Lewis, Arda-ossan, Scotmnd, assignors to imperial Chemical Industries Limited, London, England, a corporation oi' Great Britain Fied Feb. 4i, i957, Ser. No. 637,948

priority, application Great britain Feb. 3, 1956 The present invention is concerned with a new method of winning coal, rock, metal and the like in opencast working, quarrying or strip mining with blasting explosive compositions and more particularly with blasting explosive compositions containing a substantial proportion of ammonium nitrate and to apparatus therefor.

Hitherto it has been the practice to manufacture a blasting explosive composition and to cartridge or otherwise package it in a factory, to transport the cartridges or packages to the blasting site and to load the borehole with the explosive composition either in its waxed paper cartridge casing or other container or to empty the explosive composition out ot its containers into the borehole. rlhis procedure entails the observing of statutory regulations tor the production, transport and handling of explosive compositions. Since ammonium nitratel can be handied and transported otherwise than as an explosive there wouid be economic and safety advantages if the mixing of ammonium nitrate and the other ingredients forming the explosive compositions containing a substantial proportion of ammonium nitrate were delayed as long as possible, for example ir" the mixing were done in a building at the blasting site or better in the borehole itselr.

ln co-pending appiication No. 585,431, now US. latent 2,955,534 there is claimed inter alia a method of winning coal, rock, metal and the like in opecast working, quarrying or strip mining comprising forming in a substantially vertical borehole an ammonium nitrate explosive blasting composition by introducing into it concurrently and at a predetermined rate at least one stre' of ammonium nitrate and at least one Stream in so d form containing' the other ingredients of the blasting explosive composition so that the streams co-mingle during their descent in the borehole.

According to the present invention the method of winning coal, rock, and the lil-:e in opencast Working, quarrying or strip mining comprises forming in a substantially vertical borehole an ammonium nitrate blasting explosive composition containing non-explosive organic liquid uel by introducing separately into the borehole as loose solid particles the solid portion of the ammonium nitrate blasting explosive composition and as liquid the non-explosive organic liquid fuel portion so that the liquid portion is distributed through the loose soli-:l portion.

lf said solid portionV contains any solid' ingredient additional to theV animen in nitrate this preferably nonexplosive in character and maybe either mixed with the ammonium nitrate before or mixed with it during their introduction concurrently and at a predetermined rate into the borehole; the latter procedure is preferable` if the additional solid ingredient is of oxidisable character,

The liquid portion may be introduced into the borehole either concurrently with the solid portion consisting of ammonium nitrate and any additional solid ingredient or concurrently during the concurrent introduction of the ammonium nitrate and the additional other solid ingredients or the liquid portion may be introduced after the solid portion, consisting of ammonium nitrate or mixture of ammonium nitrate and any other solid ingredient, is in the desired position in the borehole.

if the liquid portion is introduced concurrently with the solid or solids it is desirable to admit said liquid portion in the form of a tine spray directed onto the descending solid particles.

it" the liquid is introduced after the borehole is charged with the required amount of ammonium nitrate and any other solid ingredients it is desirable to deliver said liquid through a pipe having a. plurality of exit orifices which are in various positions in the solid portion of the explosive composition in the borehole.

ln accordance with an embodiment of the invention protection of the water-soluble ammonium nitrate from moisture in wet boreholes can be achieved by inserting into the borehole prior to the introduction of the arnrnonium nitrate a tube of any suitable waterproof material sealed at its lower end, which if necessary may be protected against mechanical damage on the rough side of the borehole by the use of a borehole liner interposed etween the surface of the borehole and the waterproof tube which may be for example of waterproofed laminated paper or cardboard. lf desired the tube may be closed at its upper end after being loaded.

Apparatus for the carrying out of that embodiment of the process or" the invention in which there is the concurrent delivery of the solid and liquid portions of the explosive composition comprises a pipe adapted to deliver into the borehole the solid portion of the explosive composition either under gravity or by any other form of propulsion and at least one pipe adapted to deliver into the borehole the liquid portion wherein said pipes are so disposed with respect to each other that the particles of the solid portion are wetted by and substantially mixed with said liquid portion in the course of their concurrent descent into the borehole. The orices of the pipe for said liquidV portion are preferably such as to permit the liquid portion to be delivered' in finely diided form.

Apparatus for the carrying out of that embodiment of the process of the invention in which there is the successive admission of the solid portion and the liquid portion of the explosive composition intov the borehole comprises at leastA one pipe of small diameter having a plurality of orices in one end portion and adapted for insertion substantially vertically into a borehole loaded with the solid ingredients so that the oritices of said end portion are substantially distributed throughout the column of the solid ingredients.

By way of example two embodiments ofthe invention will be described with reference to the diagrammatic drawings` accompanying the speciiioation.

FGURE l is a longitudinal axial section through one form of apparatus according to the invention. The solid ingredients in loose particle form are contained in a hopper i and are metered into a vertical tube 2 by means ot a screw conveyor 3' situated coaxi'ally iny a pipe 4. Concurrently the liquidv portion of the explosive composition is delivered through a spraying device d fitted with a rose 6. In this manner the explosive composition 7 is produced in the borehole 3 into which has been inserted a tube of waterproof material 9 sealed at' its lower end.

FIGURE 2 is a longitudinal axial section through another form of apparatus of the invention. A tube lil having a plurality of orifices ll is inserted centrally in a vertical borehole S lined with a tube of waterproof material 9 sealed at its lower end. The borehole S is loaded with the solid portion of the explosive composition 7 to a depth so as to cover the uppermost orifices l1 and thereafter the liquid portion is discharged from said ori- 3 ces 11 and thus distributed in said solid portion by introducing the liquid portion into the top end of said tube 10.

In the aforementioned embodiments of the invention 4the detonation of the explosive composition produced in the borehole is initiated by a primer cartridge of for example a gelatine explosive positioned on said composition before earth is stemmed tightly into the borehole in the usual manner. The primer cartridge is initiated by a length of detonating fuse. `One end of the detonating fuse is connected to the primer cartridge and the other protrudes from the borehole. The primer cartridge may be advantageously somewhat heavier than the smallest that will initiate the detonation of the explosive composition in the borehole. For example the primer cartridge may be a 5 in. X 5 lb. charge of Opencast Gelignite for an explosive composition capable of being initiated by a 5 in. X 2 lb. charge of Opencast Gelignite.

Examples of ammonium nitrate blasting explosive compositions for which this invention is particularly suited are as follows:

Example 1 by weight Ammonium nitrate 94.6 Parafn oil 5.4

The explosive composition has a power of 75% blasting gelatine when measured on the ballistic mortar and detonates at a velocity of approximately 3,000 metres/ sec. in a 5 inch or 7 inch diameter column when initiated by a 2 lb. gelignite primer.

Example 2 by weight Ammonium nitrate 94.3 Bitumen (1 part by Weight) l 5 7 Paraiiin oil (6 parts by weight] The explosive composition has a power of 82% blasting gelatine when measured on the ballistic mortar and detonates at a velocity of approximately 3,000 metres/ sec. in a 51/2 inch diamet-er column when initiated fby a 2 lb. gelignite primer.

Example 3 by weight Ammonium nitrate 91 Mononitrotoluene 9 The explosive composition has a power of 83% blasting gelatine when measured on the ballistic mortar and detonates at a velocity of approximately 3,500 metres/sec. in a 5 inch diameter column when initiated by a 2 lb. gelignite primer.

Example 4 by weight Ammonium nitrate 86.5 Aluminium 7.5 Orthonitrotoluene 6.0

. l disulphonic acid of dinaphthyl methane as described and claimed in Specification No. 743,602 92 Woodmeal 4 Paran oil 4 The explosive composition has a power of 82% blasting p gelatine when measured on the ballistic mortar and detonates at a velocity of approximately 3,500 metres/ sec. in a 5 inch diameter column when initiated by a 2 lb. gelignite primer.

What we claim is:

l. A method of winning coal, rock, metal and the like in opencast working, quarrying or strip mining which comprises forming in a substantially vertical borehole an ammonium nitrate blasting explosive composition containing no more than about 9% non-explosive liquid and at least about 86.5% ammonium nitrate by introducing into the borehole, as loose solid particles, said ammonium nitrate and an additional solid ingredient separately and concurrently and at a predetermined rate so that said ammonium nitrate mixes with said additional solid ingredient, and separately introducing concurrently into the borehole as liquid a non-explosive organic liquid fuel, which is liquid at atmospheric conditions, so that said liquid is distributed through said ammonium nitrate and said additional solid ingredient.

2. A method of winning coal, rock, metal and the like in opencast working, quarrying or strip mining which comprises forming in a substantially vertical borehole an ammonium nitrate blasting explosive composition containing no more than about 9% non-explosive liquid and at least about 86.5% ammonium nitrate by introducing separately into the borehole as loose solid particles the solid portion of the ammonium nitrate blasting explosive composition and as liquid a non-explosive organlc liquidfuel portion, which is liquid at atmospheric conditions, so that the liquid portion is distributed through the loose solid portion, and said liquid portion of the explosive composition being introduced into the borehole concurrently with the solid portion.

3. A method of winning coal, rock, metal and the like in opencast working, quarrying or strip mining which comprises forming in a substantially vertical borehole an ammonium nitrate blasting explosive composition containing no more than about 9% non-explosive liquid and at least about 86.5% ammonium nitrate by introducing into the borehole, as loose solid particles, a previously mixed composition comprising said ammonium nitrate and an additional solid ingredient concurrently and at a predetermined rate so that said ammonium nitrate mixes with said solid ingredient, and separately introducing concurrently into the borehole a non-explosive organic fuel which is liquid at atmospheric conditions, so that said liquid is distributed through said ammonium nitrate and said solid ingredient.

References Cited in the le of this patent UNITED STATES PATENTS 2,069,612 Kirst et al. Feb. 2, 1937 2,398,071 Barab Apr. 9, 1946 2,704,515 Barlow Mar. 22, 1955 2,886,424 Hyslop May 12, 1959 2,903,969 Kolbe Sept. 15, 1959 FOREIGN PATENTS 44,422 Germany Aug. 29, 1888 725,371 Great Britain Mar. 2, 1955 

3. A METHOD OF WINNING COAL, ROCK, METAL AND THE LIKE IN OPENCAST WORKING, QUARRYING OR STRIP MINING WHICH 